The use of healthy seed is essential for good yields and quality. Be absolutely certain that the seed you are using is relatively free of major diseases and pests. As a general rule, use only certified seed. Certified seed is inspected by professionals and considered to meet certain strict standards. For example, certification almost invariably prohibits the known presence of bacterial ring rot, root-knot nematodes and certain other diseases which can lead to devastating crop losses. Strictly enforced tolerances have been established for other lesser pests and diseases. 

Certification is not a guarantee of quality. Certification reports typically emphasize what is seen during visual field inspections. Diseases present at low levels during inspection may go unobserved, increase dramatically before harvest, and lead to seed tuber infection levels far beyond tolerances. To guard against this problem, most states require some type of winter grow out test in which a small sample of each seed lot is planted and grown out for further visual inspection. Winter testing requirements vary considerably among states and among generations within states.

Factors other than field diseases can also affect the performance of seed. Remember, seed certification is primarily field oriented with some follow-up in winter grow out and laboratory tests. Seed handling during harvest, storage, and shipping may have more influence on crop performance than disease readings reported by certification inspectors. Seed should be carefully examined for excessive mechanical injury, decay, sprouting and shriveling before accepting delivery. Remember, when you accept delivery, the seed is yours along with all of the associated problems. If you have questions about quality, call in local experts for third party inspections. Keep in mind that poor seed performance may lead to lawsuits.

Seed which has been stored too warm or produced under adverse field conditions may look sound and vigorous but be physiologically "old." Old seed typically emerges, tuberizes and matures early, produces many stems and tubers, and may have lower yields than "young" seed, especially in long season locations. Physiological age of seed can be partially compensated for by changes in cultural management. On the other hand, physiological age of seed can be tailored to local needs. For example, "old" seed may be highly desirable in short season or seed production situations where early maturity or small tuber size are preferred.

A close, long-term working relationship with a few dependable seed growers is probably the best overall guarantee of consistently good seed quality year after year. By comparison, dealing with new suppliers can be dangerous. Most seed grower take care of their regular customers first and save whatever is left for new and/or late contacts (you). When dealing with new seed suppliers, on-farm visits during both the growing season and shortly before shipping are highly desirable. Also, a conscientious effort to obtain certification records and learn something about the grower's reputation is highly advisable.

Strong fences make good neighbors; so do written contracts. Make certain transaction details are clearly spelled out by using a Seed Sale Contract (under P.A.C.A. Regulation Sec 46.43). We apologize for the poor quality of the sample document provided here; steps are being taken to obtain an improved base copy from the original authors. It is somewhat usable (some imagination required) in its current printed form because of the pdf format.

U.S. seed certification agencies typically recommend use of some version of the North American Seed Health Certificate which can be extremely useful in quantifying seed quality. Most good seed growers will also enthusiastically welcome the use of such forms. You will need to obtain a printed copy (using the preceding link), fill in the grower name, variety and seed lot along with your mailing address and send the form to your local state certification agency for completion. Because of the extreme importance of winter testing for viruses, be certain to obtain final certification readings which are typically available in early to mid winter. All U.S. certification agencies provide such readings but some do not reject seed lots based on winter tests. This means, of course, that "certified" seed lots can contain a much higher level of viruses than some certification standards imply at first glance.

Time invested in finding and purchasing good seed is obviously time well spent whether dealing with familiar or new trading partners. Seed prices vary and growers may plant up to a ton per acre at common spacings (Table 1). The temptation to shave corners and take chances can obviously be troublesome. In such situations, bear in mind that "Good seed doesn't cost, it pays" in terms of yield, quality and profits.

Table 1. Approximate Cwt. of Seed Required to Plant an Acre Using 34 inch Rows 1
Seed Seed Piece Weight, Oz.      
Spacing, In. 1 1.5 1.75 2
6 19.2 28.8 33.6 38.4
8 14.4 21.6 25.2 28.8
10 11.4 17.4 20.4 22.8
12 9.6 14.4 16.8 19.2
15 7.8 11.4    

1 For 36 inch rows, multiply by 0.93

A Seed Buyer’s Checklist

  •     Use certified seed, preferably early generation stocks.
  •     Establish cordial, long-term relationships with 2-3 good seed suppliers.
  •     Consider planting seed lots of each variety from more than one supplier.

If R. Burbank from one supplier does poorly, for example, another lot from another grower is available for comparison.

  • Carefully check the reputation(s) of new suppliers.
  • Visit prospective seed lots in the field and in storage.

When visiting farms, look for sound, healthy seed/crops and a neat, clean overall physical operation. Quiz the grower about cultural practices, kill down dates, yields and so on. Killing vines late to maximize seed yield is not necessarily beneficial to you.

  • Be aware of unusual production problems (excess PVY, late blight, severe freezes etc.) in production areas you are looking to for seed.
  • Obtain all certification records, including results of winter grow outs.
  • Develop and use a written Seed Contract specifying grade, quality, delivery & payment schedules, price, etc.

The NPC developed a “Universal Seed Contract” several years ago which is still widely used.

  • Ask suppliers to provide North American Seed Health Certificates, or equivalent, for questionable lots.

These “certificates” are prepared by seed certification agencies and are, therefore, unbiased. They contain detailed information on certification readings, history, and more. You will need to send a copy of the form along with grower, variety and lot identification to your local seed certification office.

  • Ask for a federal/state or other good third party shipping point inspection of each load or seed lot.

Most U.S. states require such inspections; be certain of the situation for your seed.

  • Never forget that seed physical condition at planting can be critical!

Mechanical injury and associated decay organisms (Fusarium, Erwinia, etc.), sprouting and shriveling can be more detrimental to crop performance than all certification disease readings combined!

  • Inspect seed carefully before accepting delivery.

After you accept delivery, you've not only bought the seed but also all its problems! Never sign off until you've thoroughly checked the load for mechanical injury, decay (Fusarium dry rot, soft rots, other), shriveling, sprouting, grade, size distribution, cleanliness and other factors affecting performance. If problems seem to be present, notify your supplier. Depending on his response, immediately call in your local commodity inspection service (in Oregon, contact the ODA Commodity Inspection Division – ph. 503-986-4620) for a second inspection and a ruling on compliance. If inspectors agree with your assessment, or even if they don’t and you remain concerned, call in other local experts for unbiased third party opinions. Document everything!

  • If seed problems are evident and verified, provide the grower an opportunity to make amends before proceeding further.
  • Maximize seed performance by storing, cutting and planting carefully.

At least half of all seed performance problems are caused by events occurring after delivery. Never store seed in a cellar recently treated with sprout inhibitors! Don't suffocate, dry out, or overheat seed before or after cutting. Cut, treat and plant shortly afterward in warm (>45F), moist soil when possible. Don't irrigate before emergence in normal situations!

  • Maintain seed lot identity throughout the season.

Keep good records of all cutting and planting sequences and field locations for each lot.

  • Sanitize cutters and other handling equipment between lots.

Cutting and planting sequence and sanitation records can be crucial in lawsuits spawned by bacterial ring rot.

  • If seed disputes arise either before or after planting and emergence, call in local experts for third party input.

As noted above, allow your grower/supplier first opportunity to rectify the situation. Use the legal system only as a last resort.

  • Think long-term, beyond the current season, when dealing with seed suppliers.
  • Always strive to be a good trading partner.